It is known in the art to electrolytically extract magnesium metal from an aluminum-magnesium scrap alloy through a process referred to as electrolytic demagging. This process is performed in an electrolytic demagging cell containing a molten salt bath, typically composed of magnesium chloride (MgCl.sub.2) and various other salts, such as calcium chloride (CaCl.sub.2), potassium chloride (KCl) and sodium chloride (NaCl). Conventionally, the aluminum-magnesium scrap alloy forms the anode for the electrolytic process, while the cathode is formed of a mild steel structure. The magnesium within the aluminum-magnesium anode is electrolytically oxidized to produce magnesium cations which dissolve in the electrolyte at temperatures between about 700.degree. C. and about 750.degree. C. The magnesium cations are then reduced at the cathode such that droplets of molten magnesium metal (Mg) are deposited on the cathode. Accordingly, the net reaction is the electrolytic transport of magnesium from its aluminum-magnesium alloy at the anode to its pure state at the cathode.
In order to recover the molten magnesium metal, the electrolyte is formulated to have a density which is greater than that of magnesium, such that the molten magnesium will float to the top of the electrolyte and form a layer which can be recovered mechanically. However, a significant problem with the process described above is that the droplets of molten magnesium which are deposited on the cathode do not readily coalesce to the extent necessary to form a mass of molten metal which will float to the surface of the electrolyte. The droplets do not coalesce because of solid magnesium oxide (MgO) present in the electrolyte, which forms a film on the surfaces of the molten metal droplets. Magnesium oxide, which is practically insoluble in the electrolyte, results principally from the reaction of magnesium chloride with water in the electrolyte, as well as any other source of oxygen, such as the atmosphere or the aluminum-magnesium scrap metal. Because the magnesium droplets do not coalesce, they tend to spread throughout the electrolyte, causing short-circuiting between the anode and cathode, which may ultimately lead to cell failure.
Thus, it would be desirable to provide an electrolytic demagging process by which the magnesium oxide film on the magnesium droplets is destroyed and/or magnesium oxide present within the electrolyte is dissolved and electrolyzed, so as to enable the magnesium droplets to coalesce and float as a continuous molten layer on the top of the electrolyte. In particular, it would be desirable if such a process was accomplished in situ by eliminating the magnesium oxide in the electrolyte, in which the electrolyte is regenerated as necessary, in order to provide an economical electrolytic demagging process suitable for use in the industry.